Summary:
With the development of computer network technology, global communication technology and high-precision precision processing industry, the requirements for power supply are getting higher and higher. To ensure the reliability and stability of power supply, UPS is being applied more and more widely in various fields of the national economy. This paper introduces a fully digital UPS design method based on Motorola's single-chip MR16. A prototype is made according to the design idea, and good experimental results are obtained.
Main circuit design
The main circuit of the system mainly includes three parts: battery, inverter circuit and switching circuit. The inverter part adopts voltage type full-bridge inverter structure, as shown in Figure 1. The battery voltage is inverted by the full-bridge inverter circuit, and then boosted and filtered by the power frequency transformer. The inverter voltage or the grid voltage Un supplies power to the load through the switching switch. The system design requirements are DC side input voltage 220V, rated AC output voltage is 220V/50Hz, and rated capacity is 5kVA.
It can be seen from Fig. 1 that a closing soft-start circuit composed of R and a relay KM1 is designed between the battery and the filter capacitor, in order to prevent the inrush current generated by the battery charging the Electrolytic capacitor C1 at the moment of starting. KM1 is controlled by single-chip microcomputer. Usually, the MCU delays for a period of time after reset. After detecting the DC bus voltage reaches a certain value, KM1 is pulled in, short-circuited to the current-limiting resistor R, and the soft-start is completed. The delay time is generally 3~ 5 times the charging time constant of capacitor C1. C1 is a large filter capacitor on the DC side, which can effectively reduce the ripple AC amplitude in the DC bus voltage during operation, and can store the feedback energy storage feedback when the switch is operated for a short time, and suppress the overvoltage caused thereby. C2 is a high-frequency non-polar filter capacitor because the equivalent series impedance of the electrolytic capacitor in the high-frequency inverter circuit affects the energy absorption of the switching current. Therefore, it is necessary to parallel the capacitor at both ends of C1.
Figure 1 system main circuit
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Semiconductor Parts
Semiconductor Parts
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